a question about certain scissors

does anyone know whats the name of the scissors whose blades are zig-zagged, and more importantly, what they are used for?

There may be two types of scissors of which you're thinking. Larger, thicker scissors are called pinking shears, like Debbie stated. I use them to cut fabric because the scissors have tiny "triangles" cut out all across the edge of the blade. The idea is that fabric is less likely to ravel if it's cut like that instead of in a straight line.

There are also some scissors that are meant to cut hair which are much smaller than pinking shears that kind of look look regular scissors with little notches cut out of them. I'm not sure what they're called now, but they used to be called "thinning shears." If someone has extremely thick hair in one area and doesn't want it shorter but just less thick, the thinning shears cut out some of that bulk.